Drain pineapple, reserving juice; set aside. In a skillet, stir-fry ham until golden. In a bowl, combine brown sugar and cornstarch. Stir in water, vinegar, mustard and pineapple juice until blended. Add to the ham; bring to a boil. Reduce heat; cook and stir for 2 minutes or until thickened and bubbly. Add green pepper and pineapple; simmer for 5-8 minutes. Serve over rice.